An MRI apparatus applies to a subject placed in a static magnetic field space a high-frequency magnetic field to cause nuclear magnetic resonance (hereinafter referred to as NMR), obtains a generated NMR signal, and performs image reconstruction, thereby providing a subject image. In order to append location information to the NMR signal, a gradient magnetic field that causes an intensity gradient in three axis directions perpendicular to one another is superimposed on the static magnetic field.
For the improvement of imaging processing capability, development of a new imaging function and other purposes, a need for a higher intensity and faster switching speed of the gradient magnetic field exists. However, one problem is that, when a large current is applied to a gradient magnetic field coil, the coil generates heat. For example, Patent Document 1 discloses an MRI apparatus in which, in order to prevent a resin sealing a gradient magnetic field coil from being damaged by the heat generated from the coil, the temperature of the coil is measured and, when the temperature reaches a predetermined temperature lower than the heatproof temperature of the sealing resin, imaging will be inhibited. Patent Document 2 discloses an MRI apparatus in which, in order to prevent the temperature of the gradient magnetic field coil from reaching a predetermined temperature, while imaging, at which imaging may not be continued, the temperature increase during imaging is predicted.
On the other hand, Patent Document 3 discloses a method for solving a problem of an iron york included in a static magnetic field generating magnet being deformed by thermal expansion to cause the static magnetic field homogeneity to change, by measuring the temperature of the magnet to control current to be supplied to the shim coil.